Recently, dual-energy CT imaging technology has been playing an importance role in various fields like security inspection, lossless detection and medical treatment, as it can achieve optimal detection accuracy and enable efficient object reconstruction and material identification.
There are currently two primary implementations for a dual-energy CT imaging method. One of the implementations is a pseudo dual-energy system which performs dual-energy imaging with specifically designed double-tiered detectors, as shown in FIG. 1. In the system of FIG. 1, when scanning is performed, rays penetrate through an object and first arrive at the first tier of low-energy detectors. Then, the rays transmit filtering sheets and finally arrive at the second tier of high-energy detectors. At the same time, respective pixels of two resultant transmission images are automatically in correspondence with identical ray paths.
The other implementation is a real dual-energy system which performs circular scanning on an object using ray sources of different energy levels, as shown in FIGS. 2A and 2B. During the first round of scanning shown in FIG. 2A, the object is scanned with rays at a first energy level. Then, the rays are switched from the first energy level to the second energy level. During the second round of scanning shown in FIG. 2B, the object is scanned with rays at the second energy level. The method shown in FIGS. 2A and 2B requires radiation dose and scanning time two times more than a single-scanning method. Image matching is also required between transmission images of low and high energy levels to ensure pixels of the two images at the same coordinate correspond to the same ray path.
From the perspective of engineering realization, however, the system of the above first implementation is expensive and thus hard for wide application, due to the need for simultaneous collecting by two tiers of detectors. The second system has strict requirement on matching of transmission images between low and high energy levels. Further, the second system takes longer time due to a slow scanning speed and large scanning dose for the object due to the additional second round of scanning. These shortcomings adversely affect the popularization of dual-energy CT imaging technology.